and then the value column.
or tab_FF, tab_FG etc. for the each map tab.

You can use .csv,(comma separated files), saved from your spreadsheet program or load them from a public a Google Docs spreadsheet.

Upload your map, it will make your aware of any problems, and once you have those fixed, you can preview the map and changed the colours and range settings for you data and then share the link to the map or copy the embed code for your own site.

Time by heat maps has been available from the site, by adding a time column, and you can use an address column to automatically place addresses on heatmap, these have been available for a while but its hard to find good data to use for Ireland, geocoding still presumes addresses are in American so I suggest using Batchgeo, which you can restrict results to Ireland and review and correct and hand place some of the erroneous results. Most info is done by constituency, county or council so this should make it easier to to find data to apply. Animated time by heat map example